Lead Titanate Thin Films Research Articles

Growth and characterization of tetragonal bismuth ferrite–lead titanate thin films

Thin films of tetragonal bismuth ferrite–lead titanate (1−x)BiFeO3–xPbTiO3 with x=0.9–0.7 were prepared by pulsed laser deposition (PLD). The films exhibit a dense columnar grain growth. XRD analysis reveals that the films have a perovskite structure and exhibit a preferred (111) texture. The film microstructure was studied using SEM. The ferroelectric properties of the films are discussed in the light of polarization-field hysteresis behaviour and impedance spectroscopy. The remanent polarization values ranged between 2Pr∼45 and ∼60μCcm−2 at a field amplitude of 500kVcm−1 and −10°C, while the dielectric permittivity of the films ranged between 375 and 1096 at a frequency of 2kHz.

Parameters of Domain Boundaries in Thin PbTiO3 Films

Features of polarization switching processes in lead titanate thin films were investigated. The films under discussion were synthesized by plasma-enhanced magnetron sputtering of titanium and lead on Al 2 O 3 substrates in an argon medium, and subsequent annealing in an oxygen atmosphere. In terms of theory of lateral motion of domain boundaries the main parameters of domain walls, characterizing kinetics of domain structure in thin polycrystalline lead titanate films, were determined.

Deposition of PbTiO 3 films on Pt/Si substrates using pulsed laser deposition

Lead titanate (PbTiO 3) thin films were prepared on platinised silicon substrates by pulsed laser deposition. A predominantly (1 1 1) oriented perovskite phase was obtained at a substrate temperature of 530 °C. Deposition at higher substrate temperatures resulted in the formation of a lead deficient pyrochlore phase PbTi 3O 7. The (1 1 1) orientation was slightly enhanced with an increase in the oxygen deposition pressure from 100 mTorr to 150 mTorr. A similar effect was observed with an increase in the post-deposition annealing temperature from 400 °C to 600 °C. P– E loops with remanent polarization ( P r) as high as 40 μC/cm 2 and coercive field E c = 105 kV/cm were obtained under an electric field of an amplitude of 270 kV/cm at 50 kHz. Impedance spectroscopy and leakage current behaviour of the films are also reported.

Electrical properties of thin lead titanate films on polycor substrates

The dielectric properties of synthesized films, including the permittivity dispersion, have been investigated. The fatigue processes in the films have been experimentally studied as a function of the number of cycles of external voltage switching. It is established that the main dielectric characteristics are partially recovered in the absence of external actions.

Large remanent polarization in ferroelectric BiFeO3–PbTiO3 thin films on Pt∕Si substrates

Bismuth ferrite–lead titanate thin films in the region of the morphotropic phase boundary, with compositions of (1−x)BiFeO3–xPbTiO3 (0.3<x<0.5), were prepared by pulsed laser deposition on Pt∕Si substrates. X-ray diffraction confirmed the formation of pure perovskite phase at a substrate temperature of 565°C under 75mTorr of oxygen. The films exhibit remanent polarizations with 2Pr up to 100μCcm−2 for a field amplitude of 820kVcm−1 and switchable polarization up to 80μCcm−2.

The fabrication and characterization of (Pb,Ca)TiO3 pyroelectric thin films with different Ca contents

This study uses radio-frequency sputtering methods to deposit lead titanate thin films with different contents of Ca on Pt∕Ti∕SiO2∕Si substrates to form Pb1−xCaxTiO3 (PCT) thin films. The PCT thin films contained different amounts of Ca in order to examine the influence of the Ca content on the properties of thin films. Analysis of the electrical properties of the PCT thin films revealed that their relative permittivities, dissipation factors, and pyroelectric coefficients tend to increase with the Ca content. On the other hand, the coercive field and remnant polarization decreased with an increase in the Ca content. In addition, the measured data indicated that the figure of merit for voltage (Fv) and the figure of merit for detectivity (FD) of a PCT (30) thin film are the highest with values of 0.033m2C−1 and 0.862×10−6(m3J−1)1∕2, respectively. Therefore, the PCT (30) thin film was evaluated as the best composition for manufacturing pyroelectric infrared (PIR) sensors. PCT thin films were also used to fabricate thermal PIR sensors by surface machining technology. The detectivity measurement showed that the PIR sensor with PCT (30) thin films has the highest value of D* (1.29×107cmHz1∕2∕W) at 0.3Hz.

Processes of Ageing and Fatigue in Lead Titanate Thin Films

Processes of ageing and fatigue in lead titanate thin films are experimentally investigated. The films under discussion were synthesized by plasma-enhanced magnetron sputtering of titanium and lead on titanium, silicon and polycor substrates in an argon environment, and subsequent annealing in an oxygen atmosphere. High temperature resistance, long shelf ageing and repolarization stability of lead titanate films on polycor substrates was shown. Reduction of polarization under cyclic switching in sine wave electric field to the minimal value happens after 10 11 cycles. Partial recovery of the basic dielectric characteristics of lead titanate thin films was observed during relaxation without external influences.

Compound two-dimensional thermo-elastic and thermodynamic analysis for c-axis-oriented epitaxial lead titanate thin films

We propose two-dimensional (2D) thermo-elastic model to predict the temperature variation of the lattice constants and volume loss of the epitaxial (0 0 1)PbTiO 3 (PT) thin films grown on (1 0 0)SrTiO 3 substrates under specific biaxial stress conditions. The stresses resulted from the induced thermal stress and thermo-elastic bending of the PT film and ST substrate are used together with the external stresses to calculate the Landau–Ginsburg–Devonshire (LGD) formalism for PT at any temperature. The dielectric constant and spontaneous polarization could be accurately determined under compound effect of 2D state of stress and temperature variation. Because this study combines thermodynamic with thermo-elastic mechanics; it would be very useful for design and simulate the performance of piezoelectric micro-sensors and micro-actuators which are usually subjected to a various heat and stress under actual working conditions. The present predictions are applicable for a fabrication of piezoelectric MEMS on Si wafers.

Thickness Dependence of Residual Stress in Alkoxide-Derived Pb(Zr0.3Ti0.7)O3 Thin Film by Chemical Solution Deposition

Ferroelectric thin films of Pb(Zr0.3Ti0.7)O3 (PZT30) with different thicknesses were deposited on a Pt/Ti/SiO2/Si substrate by chemical solution deposition (CSD). The residual stress in the PZT30 thin films was estimated by the phonon mode shift of Raman scattering. The stress dependence of the optical phonon mode of ferroelectric tetragonal PZT30 was calibrated by a gasketed diamond anvil cell (DAC) system. As a result, the A(2TO) mode for PZT30 was downshifted at a rate of 13.9 cm-1/GPa. By using this calibration result, the residual stress in the PZT30 thin films with different thickness was estimated. The residual stress in PZT30 thin films increased with decreasing film thickness and reached approximately 1.14 GPa in the case of a film 280 nm thick. Moreover, the residual stress in the PZT30 thin films was compared with that of a lead titanate (PT) thin film to discuss the origin of the residual stress.

Dispersion of Dielectric Permittivity in Thin Ferroelectric Lead Titanate Films

Lead titanate thin films were obtained by plasma-enhanced magnetron sputtering. Synthesized films demonstrate high temperature stability, relatively narrow maximum at temperature of phase transition for ε (T ) dependence, great dielectric constant value near the Curie point, saturated hysteresis loops, and relaxation character for dispersion of dielectric permittivity similar to bulk samples.

The effect of biaxial texture on the effective electromechanical constants of polycrystalline barium titanate and lead titanate thin films

Effective electromechanical constants as a function of biaxial crystallographic texture in polycrystalline films are modeled using a self-consistent approach. The film is modeled by assuming Gaussian distributions of two Euler angle textures about perfect orientation with varying spread, or full width at half maximum. We see that independent in-plane texturing has little effect on the piezoelectric displacement tensor. Increased out-of-plane texturing gives rise to an enhanced piezoelectric effect for barium titanate films, but not for lead titanate. Twist texturing about these out-of-plane angles shows a further enhancement in the non-shear components of the piezoelectric displacement tensor for both materials. Finally, we use the effective piezoelectric coupling factor as the primary figure of merit for the effective piezoelectric properties of polycrystal devices, thus utilizing all electromechanical constants of this simulation. This quantity shows a primary dependence on the out-of-plane texture.

Dielectric properties of lead titanate thin films on corundum substrates

Ferroelectric films of lead titanate were synthesized on corundum (Al2O3) substrates. The main parameters that characterize the dielectric hysteresis, such as the spontaneous polarization, coercive force, internal bias field, and the phase-transition temperature, were determined. The dispersion of the permittivity was studied using impedance spectroscopy in wide temperature and frequency ranges. An anomaly in the frequency dependence of the complex permittivity was revealed at frequencies of the order of 107 Hz.

Development of a piezoelectric lead titanate thin film process on silicon substrates by high rate gas flow sputtering

Polycrystalline lead titanate (PT) thin films in the range of 3–6 μm were crack and void free deposited on silicon substrates in a high rate gas flow sputtering process. Gas flow sputtering uses the hollow cathode effect which results into high deposition rates of about 120 nm/min. (1 1 1) Textured platinum was used as bottom electrode to assist the nucleation of PT. Material properties of the PT thin films as well as the Pt bottom electrode like topography, morphology, chemical composition, and structure are evaluated. The sputtered PT layers show clearly Perovskite traces in XRD patterns, even the (1 1 1) texture of the Pt is partial transferred. The most difficult part is to fulfil the empirical formula PbTiO 3. This problem is solved by stabilising the process parameters. It was shown that the temperature has got enormous influence at the stoichiometry.

Growth and structure of heteroepitaxial lead titanate thin films constrained by miscut strontium titanate substrates

Single-crystal lead titanate [(001)PbTiO3 (PT)] thin films were heteroepitaxially grown on a miscut strontium titanate [(001)SrTiO3 (ST)] substrate by radio frequency magnetron sputtering. The PT thin films were grown via a step-flow growth. The step-flow growth enhanced the layer growth resulting in the continuous (001) single-crystal structure without a dislocated interface for the film thickness below 200 to 250 nm. The PT thin films show a small temperature variation of the lattice parameters unlikely to the bulk PT crystals due to the substrate clamping. The temperature variation of the lattice constants is discussed in terms of the thermo-elastic deformation analysis for the PT/ST heterostructure.

Piezoelectric property of an epitaxial lead titanate thin film deposited by the hydrothermal method

A PbTiO3 epitaxial thin film was deposited at 150°C at a thickness of 430nm. The domain structure was composed of c domain and small amount of a domain. The DE hysteresis curve and piezoelectric strain curve were asymmetrical because the initial domain structure was stable and difficult to reverse perfectly with an external electric field. The strain has exceptional linearity, and the d33eff coefficient was found to be 97pC∕N, which is larger than the theoretical value.

Structural and dielectric properties of Er substituted sol-gel fabricated PbTiO3 thin films

Er substituted lead titanate thin films were processed via chemical solution deposition. Their structural properties were investigated by means of atomic force microscopy, X-ray diffractometry and micro-Raman spectroscopy. The Curie temperature, TC, was obtained from dielectric measurements. The results show that the grain size, tetragonality factor, c/a, E(1TO) transverse optical phonon frequency and the ferroelectric-to-paraelectric phase transition are affected by Er doping. Particularly the lattice tetragonality and Curie temperature of Er substituted films are found to be substantially lower in comparison to undoped specimen. In contrast, the E(1TO) phonon frequency is only slightly reduced by Er doping. The Results obtained for pure and Er substituted specimens are discussed in terms of combined effects of grain size, stress development and doping on the structural characteristics.

Correlation between structural and mechanical properties of PbTiO3 thin films grown by pulsed-laser deposition

Tetragonal lead titanate (PbTiO 3 , PT) thin films are grown on (1 0 0) MgO substrate by pulsed-laser deposition (PLD) for expected applications in integrated optics. The realisation of outstanding and reliable devices into integrated circuits requires sufficient mechanical resistance despite that the obtained PT films display interesting waveguiding properties associated with low optical losses. Two mechanical properties characteristic of elasticity and hardness of PT films are studied. The elastic modulus ( E or Young's modulus) and the hardness ( H ) are measured by the nanoindentation technique. These mechanical properties are correlated to the crystalline quality of PT/MgO thin films. The films show epitaxial relationship with the MgO substrate and the orientation of crystallites perpendicularly to the surface substrate may be the consequence of a growth process along c -axis, a -axis or both. Differences on curves plotting hardness and elastic modulus as a function of indentation depth are observed as the curves are less dispersed for the films mainly c -axis oriented.

Direct characterization of nanoscale domain switching and local piezoelectric loops of (Pb,La)TiO3 thin films by piezoresponse force microscopy

〈111〉 and 〈001〉, 〈100〉 preferentially oriented lanthanum-modified lead titanate thin films have been studied at the nanometre scale by means of piezoresponse force microscopy. The nanoscale domain structures, domain switching, and local piezoelectric loops of the films have been analysed. The imaging of the domain structures after the application of a dc field suggests the existence of 90° and 180° domains within the regions with intermediate contrast. The variation of piezoresponse under an electric field in domains of two types has been discussed. Significant differences have been found between the local piezoelectric loops measured in the films deposited on different substrates. These differences are related to the different textures present in the films.

Atomic layer deposition and post-deposition annealing of PbTiO 3 thin films

Lead titanate thin films were deposited by atomic layer deposition on Si(100) using Ph 4Pb and Ti(O- i-Pr) 4 as metal precursors and O 3 and H 2O as oxygen sources. The influence of the Ti : Pb precursor pulsing ratio on the film growth, stoichiometry and quality was studied at two different temperatures, i.e. 250 and 300 °C. Uniform and stoichiometric films were obtained using a Ti : Pb precursor pulsing ratio of 1 : 10 at 250 °C or 1 : 28 at 300 °C. The as-deposited films were amorphous but the crystalline PbTiO 3 phase was obtained by rapid thermal annealing at 600–900 °C both in N 2 and O 2 ambient. Thin PbTiO 3 films were visually uniform and roughness values for as-deposited and annealed films were observed by atomic force microscopy.

Enhancement of the 90° domain-wall mobility in sol-gel (Pb,La)TiO3 thin films prepared by multiple deposition and crystallization

Sol-gel lanthanum-modified lead titanate thin films deposited onto Si-based substrates with two different processing conditions have been studied. The films have been processed with a single crystallization or with a multiple deposition and crystallization process. A preferential ⟨001⟩,⟨100⟩-mixed orientation is present in the two types of films. The dependence of the dielectric permittivity on frequency and field amplitude at subswitching fields, permittivity versus temperature curves, and ferroelectric hysteresis loops have been measured in the films. Both types of films present Rayleigh-type behavior with no differences between them, which suggests a similar density of defects in both films. Higher values of remanent polarization and dielectric permittivity, when approaching the transition temperature, have been achieved for the film prepared with the multiple deposition and crystallization process when compared with the obtained ones in the film prepared with a single crystallization. This is due to a lower clamping effect and an enhancement of the 90° domain-wall mobility in the former, as a consequence of the lower residual stress present in this film, achieved by means of the multiple deposition and crystallization process.